The present invention relates generally to wireless local area network systems and more particularly to a distribution network for coupling wireless local area network signals between centrally located internetworking devices and remotely located access points.
The most common user applications for personal computers now require a connection to a computer network of some type. Such applications include the viewing of e-mail, sharing of data files, and accessing the Internet and the World Wide Web. Various techniques are used for connecting computers together so that they may send data to and receive data from each other, more or less in real time. Most often this so-called physical layer is implemented using wires and the bits of data to be exchanged are converted into electrical signals that move through the wires. Traditionally, local area networks (LANs) were implemented using privately installed wiring, such as coaxial cable or twisted pair type cable and network adapter circuits. Later, it became possible to construct LANs through the use of the public switched telephone network and modem equipment.
However, networks that use infrared light or radio frequency energy at the physical layer are growing in popularity. These so-called wireless local area networks (xe2x80x9cwireless LANsxe2x80x9d) convert the bits of data into radio waves to enable their transmission over the air, which in turn minimizes the need for hard wired connections.
Wireless LANs have tended to find application where user mobility and portability is important, such as in the healthcare, retail, manufacturing, and warehousing industries. This limited use has no doubt been the result of the added cost of the required wireless network adapters. However, they are also becoming more widely recognized as a general purpose alternative for a broad range of business applications as the cost of mobile computing equipment such as laptop computers and personal digital assistants (PDAs) continues to decrease. With a wireless LAN, users can access shared information without first stopping to find a place to plug-in their equipment. In addition, network managers can set up or augment such networks without installing or moving wires around from place to place.
The simplest wireless LAN configuration is an independent type network that connects a set of computers with wireless adapters. Anytime any two or more of the wireless adapters are within radio range of one another, they can set up a network. More common is a type of multi-user LAN wherein multiple devices referred to as access points collect signals at a central location. The access points collect signals transmitted from personal computers equipped with wireless network adapters, and distribute them over wire physical media to other internetworking devices such as repeaters (hubs), bridges, routers, and gateways, to provide interconnectivity to larger networks.
The range of a wireless LAN is limited by how far the signals can travel over the air between the access points and the network adapters connected to the PCs. Currently, the Institute of Electrical and Electronic Engineers (IEEE) 802.11 wireless LAN standard, which is the most widely used, specifies power output levels which carry signals over a few hundred feet.
To extend coverage beyond this limited range, a network of access points with overlapping radio ranges must be located throughout the desired coverage area. These so-called infrastructure wireless LANs are implemented in a manner which is similar to a cellular telephone system. At any given time, a mobile personal computer equipped with a wireless LAN adapter communicates with a single access point within the current microcell within which it is located. On the landline side, the access points are interconnected using network-compatible twisted pair wiring such as that which is compliant with the Ethernet/802.3 10baseT or 100baseT standard. The network signals can then be further forwarded to a local- or wide-area network using standard internetworking protocols and devices.
The present invention provides a simple and low cost architecture for coupling wireless local area network (xe2x80x9cwireless LANxe2x80x9d) signals between geographically distributed access points and centrally located internetworking devices. The invention eliminates complexities involved with the deployment of such systems in the past, which have typically required the computer network-compatible wiring to be extended to each access point directly from an internetworking device such as a repeater, bridge, router, or gateway.
The present invention makes it economically efficient to deploy wireless local area networking equipment in locations where wired network infrastructure is not readily available. In particular, any convenient existing physical wiring, such as may be provided by the existing coaxial cable used to distribute cable television signals, or the existing twisted pair cabling used to distribute standard telephone signals, is used as a physical layer transport medium to carry the wireless local area network signals between the access points and centrally located network hub equipment.
More particularly, a cable access point (CAP) is associated with each wireless local area network microcell. The cable access point includes access point equipment for communicating with portable computing equipment located within the microcell, such as may be provided in accordance with standard wireless network specifications such as the Institute of Electrical and Electronic Engineers (IEEE) 802.11 wireless LAN standard.
Rather than couple the wire line side of the access point directly through local area network format cabling such as 10baseT or 100baseT, a remote bridge first converts such signals to a convenient transport format. The transport format implemented by the remote bridge depends upon the available cabling.
For example, if the available cabling is a cable television (CATV) plant, the transport signals may be first converted to a digitally modulated format specified by the American National Standards Institute (ANSI) standard T1. The T1 signal is then up-converted to a carrier frequency suitable for forwarding over the available CATV plant, such as in the range of from 5-750 MHz.
Alternatively, cable modem equipment may be used in place of the frequency translation and bridging equipment.
If the available cabling is twisted pair plain old telephone service (POTS) type wiring, the remote bridge converts the transport signals to a suitable format such as Digital Subscriber Line (xDSL) format.
The transport signals are collected at a central distribution or headend access point (HAP). At this location, a remote bridge then converts the signals from the up-converted T1 format, in the case of CATV plant implementation, or the xDSL format, in the case of the twisted pair implementation, back to the wired local area network format such as Ethernet/802.3 10baseT or 100baseT. These Ethernet signals are then suitable for coupling to a local area network hub, or other internetworking equipment such as repeaters, bridges, routers, gateways and the like.
As a result, it is not necessary to deploy Ethernet-compatible or other data network cabling directly to the physical location of each access point within the desired coverage area. Rather, the access points may be deployed in configurations wherever there is available cable television wiring or telephone network wiring, without consideration for the cost and/or logistics of deploying local area network compatible cabling.